Change in microstructures and physical properties of ZrB2–SiC ceramics hot-pressed with a variety of SiC sources

Abstract

ZrB2–SiC ceramics were fabricated by hot pressing with a variety of SiC sources in order to examine the effect of the SiC size on the microstructures and physical properties, such as hardness and thermal conductivities, of ZrB2–SiC composite ceramics. Three different ZrB2–SiC ceramics, ZPS (ZrB2–20vol% polycarbosilane), ZFS (ZrB2–20vol% fine-grained SiC), and ZNS (ZrB2–20vol% nano-sized SiC), were prepared for this study. PCS is effectively transformed into β-SiC after hot pressing. By using PCS as a precursor for SiC, ZrB2 particles are surrounded by fine particles of SiC, which results in the grain-growth inhibition of ZrB2. The effects of the SiC size on the microstructures and the physical properties of ZrB2–SiC ceramics were also investigated. ZrB2–SiC ceramics were produced by using various SiC sources in order to investigate the grain-growth inhibition and the mechanical/thermal properties of ZrB2–SiC. The sizes of ZrB2 or SiC particles in the sintered bodies highly depend on the initial size of SiC. ZrB2–SiC ceramics with smaller SiC show enhanced mechanical properties, consistently with the Hall–Petch relation. The thermal conductivities of ZrB2–SiC ceramics with nano-SiC or PCS-derived SiC are higher than that of ceramics with conventional SiC, which can be explained by the percolation theory.